The existing light emitting diodes (LEDs) are obtained by mixing a green phosphor and a red phosphor with a blue light emitting diode or mixing a yellow phosphor and a blue-green phosphor with a UV light emission light emitting diode. However, in this method, it is difficult to control colors, and accordingly, the color rendition is not good. Therefore, the color gamut deteriorates.
In order to overcome the deterioration in color gamut and reduce the production costs, methods of implementing green and red colors have been recently attempted by using a method of producing a quantum dot in the form of a film and combining the same with a blue LED. However, cadmium-based quantum dots have safety problems, and the other quantum dots have much lower efficiencies than those of the cadmium-based quantum dots. Further, quantum dots have low stability against oxygen and water, and have a disadvantage in that the performance thereof significantly deteriorates when the quantum dots are aggregated. In addition, when quantum dots are produced, it is difficult to maintain the size thereof at a certain level, and thus, the production cost is high.